The present invention is deemed to be a considerable and meritorious improvement over the inventions disclosed in U.S. Pat. Nos. 4,022,479; 4,114,902; 4,175,752; 4,304,409; 4,466,620; and 4,706,968.
In many industries, it is extremely important to obtain a seal for rotating shafts emerging from a bearing and its housing which prevents the lubricants associated with the bearings from leaking externally of the associated housing or bearing support and for preventing contaminants in the environment from working themselves through the seal and into the lubricant for the bearings.
Various successful labyrinth bearing isolation devices exist in two-piece and three-piece combinations. Single-unit labyrinth sealing devices also exist. However, the single-unit labyrinth sealing devices are notoriously ineffective in dealing with contaminant intrusion, although they successfully retain lubricant.
U.S. Pat. No. 4,022,479 incorporates a disclosure wherein is taught a two-piece sealing ring structure which has an object elimination of the loss of lubricant from the bearings supporting a rotating shaft. The sealing ring structure disclosed also eliminates the movement of contaminants into the bearings and lubricant. Further disclosed in a sealing structure that is composed of two rings, preferably metal, one fixed to a housing and the other fixed to rotate with a shaft. The ring that is fixed to a housing has a labyrinth seal next to the shaft which prevents lubricant from moving outside of the housing along the shaft.
Also in U.S. Pat. No. 4,022,479, a joint is provided between the two rings which is an annular recess in the first ring and an annular flange on the second ring that fits within the annular recess of the first ring. The construction of the recess and the flange are complimentary, so that when one of the rings is rotating relative to the other, the seal will not bind or create heat by friction between them. There is also provided in the first ring member an elongated hole that communicates from the annular recess to the outside of the first ring member. In the embodiment taught in this prior patent, the annular flange of the sealing ring member has axial notches. By this means, foreign matter that migrates into the joint between the ring members is expelled from the seal. It may be noted that the second ring member is made to rotate with the shaft by suitable frictional sealing means. However, there is no rubbing, wear or contact between the sealing ring members.
The invention of U.S. Pat. No. 4,114,902 was an ingenious improvement over the device disclosed in U.S. Pat. No. 4,022,479. The improvement included one or more grooves on the outer periphery of the annular flange of the second ring member. Additionally, the accomodating recess in the other ring member also contained one or more grooves. It was also taught in U.S. Pat. No. 4,114,902 that these grooves inhibit contaminant migration, regardless of relative peripheral speed of the rotating rings and to provide a tortuous path for the exclusion of foreign material even in the event of zero relative rotation.
U.S. Pat. No. 4,175,752 disclosed a labyrinth seal comprising a single ring having both an annular gap and a primary drain. The uniqueness of the device consists in the addition of the annular gap; lubricant is prevented from migrating along the shaft for which it is used.
U.S. Pat. No. 4,304,409 disclosed an improved sealing assembly which is a liquid pressure differential seal useful with a bearing shaft and housing. The seal includes a multi-ring sealing structure fixed to the housing and between the shaft and the housing. The multi-ring structure is arranged so that a first (stator) ring is fixed to the bearing housing and a second (rotor) ring is fitted to the rotating shaft. The improvement comprises a pressure and self compensating sealing device positioned radially to the shaft. It consists of a cover and a support spring partially encapsulated by the cover.
The invention of U.S. Pat. No. 4,466,620 is a further ingenious improvement over the devices disclosed in the aforementioned patents and solves additional problems. The improvement, among other items, includes a modification of the drain hole in the first sealing ring. That hole was modified so that its length is greater than its width like an ellipse. This improvement eliminates expulsion problems which occasionally arise due to the minor relative axial displacement of the sealing rings when the drain hole is circular. It provides a more effective means to expell foreign matter from the annular recess (or recesses if more than one flange-recess combination is provided) at the interface of the sealing rings.
U.S. Pat. No. 4,466,620 also encompassed an additional improvement wherein a portion of the first ring member that faces towards the bearing located inside its housing is extended to form a shielding protrusion. This improvement keeps off the liquid lubricant that is continuously thrown at the first ring member in certain applications, e.g. multiple gear and pinion speed reduction gearing.
U.S. Pat. No. 4,706,968 is a further unique and ingenious improvement over other labyrinth seal devices in having a third ring member which is located between the interface of the first stationary ring member and the second rotary ring member in complimentary recesses in the first ring member and the second ring member.
All of the above two and three piece labyrinth seals have universal applicability but require custom manufacture and so tend to be expensive. Thus, while being widely acknowledged and accepted, there remains some hesitancy in many companies to use them. Further, with the prevalence of inexpensive rubber or synthetic lip (contact) type seals, many companies prefer not to use the aforementioned labyrinth seals. Unfortunately, rubber or synthetic rubber lip seals must be replaced frequently and are notoriously ineffective in retaining lubricant and in dealing with contaminant intrusion.
The above identified two and three piece labyrinth seals are advances which have solved a large number of problems. However, certain problems are still encountered in various particular work applications. Problems remain in cases where a large amount of lubricant splash is encountered, thus necessitating increased radial clearances on the inside surface of the rotor insertion. Further problems are encountered in cases where axial shaft movement (oscillation) occurs, as in sleeve bearing electric motors. Axial separation of the two and three piece seal components is thereby possible.
Accordingly, it would be highly desireable to have a sealing ring structure that is inexpensive, compact in design, will successfully retain lubricant within the bearing, will not require a cartridge configuration to accomodate axial shaft movement, would not have a pumping tendancy, will prevent contaminant intrusion and will have a broad range of applications.